Genetics of Achondroplasia and Hypochondroplasia

Achondroplasia and hypochondroplasia are relatively common skeletal dysplasias characterized by disproportionate short stature, rhizomelic shortening of the limbs, and increased head circumference. Short stature and body disproportion are usually severe and uniform in achondroplasia, whereas phenotype in hypochondroplasia varies from severe achondroplasia-like forms to mild shortness and body disproportion. Mild forms of hypochondroplasia are on clinical grounds difficult to differentiate from idiopathic short stature or normal height at the shorter end of the height spectrum.